The risk of venous thromboembolism in atopic dermatitis: a population-based cohort study

Atopic dermatitis (AD) is a common inflammatory skin disease. Evidence on baseline venous thromboembolism (VTE) risk is inconsistent, but a clear understanding of this risk may be crucial in disease management.

To evaluate whether individuals with AD have a higher risk of incident VTE than the general population and to assess variations in risk by demographics and disease severity.

This nationwide matched cohort study used Swedish health and population registers to examine VTE incidence in patients with AD. The study population included individuals diagnosed with AD who were aged ≥ 18 years from 1 January 2007. Patients with AD were matched by birth year and sex with up to five controls who did not have AD. AD severity was defined by use of systemic immunomodulatory treatment or hospitalization with AD as the primary diagnosis. Incidence rates per 1000 person-years were calculated for the AD cohort and the general population. Cox proportional hazard regressions were used to estimate VTE hazard ratios, adjusted for comorbidities, treatments and socioeconomic variables. Follow-up started at first AD diagnosis or 18th birthday and ended at first VTE event, emigration, death or end of study (31 December 2023).

We identified 210 492 individuals with AD. These individuals were matched with 1 048 395 controls without AD. At inclusion, 94.1% had nonsevere AD and 5.9% had severe AD. The AD cohort had 3292 VTE events, with an incidence rate of 1.49 per 1000 person-years, compared with 1.71 per 1000 person-years in the general population. VTE risk was similar in individuals with AD and the general population [adjusted hazard ratio (aHR) 1.04, 95% confidence interval (CI) 1.01-1.09]. Those with severe AD had a higher VTE risk than the general population (aHR 1.93, 95% CI 1.70-2.14). Elevated VTE risk in severe AD was seen across all age groups. The youngest group (18-39 years) exhibited a higher relative risk than age-matched controls (aHR 2.95, 95% CI 2.40-3.59).

This large population-based study found similar overall VTE risk between patients with AD and the general population, but higher risk in those with severe AD, particularly among younger adults. Further research is needed to clarify the clinical implications of these findings.